U.S. patent application number 10/540253 was filed with the patent office on 2007-01-25 for method and device for influencing combution processes of fuels.
Invention is credited to David Walter Branston, Gunter Lins, Jobst Verleger.
Application Number | 20070020567 10/540253 |
Document ID | / |
Family ID | 32667536 |
Filed Date | 2007-01-25 |
United States Patent
Application |
20070020567 |
Kind Code |
A1 |
Branston; David Walter ; et
al. |
January 25, 2007 |
Method and device for influencing combution processes of fuels
Abstract
An electrical device is used for guiding and/or altering a
flame. The flame is subjected to the action of an electric field.
Further, an insulating material enclosure made of ion-conducting
material prevents charge transfer between the flame and the
field-generating electrode.
Inventors: |
Branston; David Walter;
(Effeltrich, DE) ; Lins; Gunter; (Erlangen,
DE) ; Verleger; Jobst; (Erlangen, DE) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O.BOX 8910
RESTON
VA
20195
US
|
Family ID: |
32667536 |
Appl. No.: |
10/540253 |
Filed: |
December 12, 2003 |
PCT Filed: |
December 12, 2003 |
PCT NO: |
PCT/DE03/04121 |
371 Date: |
September 27, 2006 |
Current U.S.
Class: |
431/8 ;
434/356 |
Current CPC
Class: |
F23M 2900/05004
20130101; F23C 99/001 20130101; F23R 2900/00013 20130101; F23N
5/245 20130101; F02M 27/04 20130101 |
Class at
Publication: |
431/008 ;
434/356 |
International
Class: |
F23C 5/00 20060101
F23C005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 23, 2002 |
DE |
10260709.5 |
Claims
1. A method for influencing combustion processes of fuels,
comprising: using at least one electric device for at least one of
guiding and changing a flame, the flame being subjected to action
of an electric field; and limiting charge carrier transport, from
at least one of the flame and at least one of the field-producing
electrodes to at least the other of the flame and at least one of
the field-producing electrodes, by the fact that the flame and the
electrode are separated from each other using an ion-conducting
material.
2. The method as claimed in claim 1, wherein material and geometry
of the ion-conducting material are chosen such that a
temperature-dependent transition from the insulating to the
conductive state takes place as a result of ion conduction, the
conductivity remaining limited to permissible values in the
conductive state.
3. The method as claimed in claim 2, wherein the conductivity is
limited in such a way that the charge carrier transport is low and
the current through the flame does not exceed permissible
values.
4. The method as claimed in claim 3, wherein the charge carrier
transport is kept so low that, during the combustion process, the
occurrence of independent discharges is prevented.
5. The method as claimed in claim 1, wherein the charge carrier
transport is limited in such a way that thermo-acoustic emissions
are reduced.
6. The method as claimed in claim 1, wherein the fuel used is a
pre-mixed gas.
7. A device, comprising: at least one of stabilizing and
pollutant-reducing device for influencing the flame during the
combustion process, the device including field-producing
electrodes, at least one of the electrodes being separated from the
flame by an insulating material enclosure including an
ion-conducting material which prevents charge carriers from the
flame striking the electrode.
8. The device has claimed in claim 7, wherein the material changes
to the conductive state as a result of the ion conduction at
temperatures of a few 100 K.
9. The device as claimed in claim 7, wherein the ion-conducting
material is aluminum oxide.
10. The device as claimed in claim 7, wherein the ion-conducting
material is a zirconium oxide stabilized with additives.
11. The device as claimed in claim 10, wherein the additives are
yttrium oxide.
12. The device as claimed in claim 7, wherein the insulating
material enclosure surrounds the flame in such a way that the fuel
enters at its one end and the combustion waste gas emerges at the
other end.
13. The device as claimed in claim 7, wherein there is at least one
further electrode which is not surrounded by an insulating material
enclosure.
14. The device as claimed in claim 7, wherein the further electrode
is located inside the insulating material enclosure.
15. The device as claimed in claim 14, wherein the electrode
arranged inside the insulating material enclosure is formed by at
least one of a housing and another electrically conductive part of
the burner.
16. The device as claimed in claim 7, wherein the electrodes are at
a potential different from that of the first electrode.
17. The device as claimed in claim 7, wherein at least one of the
electrodes rests in a positive manner from the insulating material
enclosure.
18. The device as claimed in claim 7, wherein the electrodes of
different potential are separated electrically from the insulating
material enclosure.
19. The device as claimed in claim 7, wherein the insulating
material enclosure has electrically insulating leadthroughs.
20. The device as claimed in claim 7, wherein the electrodes form
toroidal annular electrodes.
21. The device as claimed in claim 7, wherein the electrodes form
cylindrical electrodes.
22. The device has claimed in claim 7, wherein the electrodes are
formed by at least one of films applied to the outside of the
insulating material enclosure and layers produced by at least one
of vapor deposition and spraying on.
23. The device as claimed in claim 7, wherein the electrodes are
connected by feed lines to a power supply unit.
24. The device as claimed in claim 23, wherein the power supply
unit supplies a direct voltage.
25. The device as claimed in claim 23, wherein the power supply
unit supplies at least one of a clocked direct voltage, an
alternating voltage and a pulsed voltage.
26. The device as claimed in claim 23, wherein the power supply
unit supplies at least one of a clocked direct voltage, an
alternating voltage and a pulsed voltage which are superimposed on
a constant direct voltage.
27. The device as claimed in claim 7, wherein there are sensors for
at least one of the frequency and amplitude of combustion
oscillations and the pollutant concentration in the waste gas
stream, the frequency, amplitude and phase of the voltage applied
to the electrode being controlled or regulated by at least one of a
control and regulating device such that the combustion oscillations
and the pollutant concentration are minimized.
Description
[0001] This application is the national phase under 35 U.S.C.
.sctn. 371 of PCT International Application No. PCT/DE2003/004121
which has an International filing date of Dec. 12, 2003, which
designated the United States of America and which claims priority
on German Patent Application number DE 102 60 709.5 filed Dec. 23,
2002, the entire contents of which are hereby incorporated herein
by reference.
FIELD
[0002] The invention generally relates to a method for influencing
combustion processes of fuels; for example one in which electric
devices are used for guiding and/or changing a flame on a burner.
In addition, the invention also generally relates to a device for
carrying out the method; for example by using stabilizing and/or
pollutant-reducing devices for influencing the flame during the
combustion process, the devices having field-producing electrodes
on the burner for example.
BACKGROUND
[0003] The advantageous influences which electric fields can have
on combustion flames have in principle been known for a long time.
According to the publications [0004] Industrial and Engineering
Chemistry 43 (1951), pages 2726 to 2731, [0005] 12.sup.th Annual
energy-sources technology conf. (1989), pages 25 to 31 and [0006]
AIAA Journal 23 (1985), pages 1452 to 1454 the actions of the
electric field consist in improving the stability of the flame.
According to [0007] Combust. Flame 78 (1989), pages 357 to 364 and
[0008] Combust. Flame 119 (1999), pages 356 to 366, a reduction in
the soot emission is provided and, according to [0009] Fossil Fuel
Combustion, ASME 1991, pages 71 to 75 and [0010] Fluid Dynamics 30
(1995), pages 166 to 174 a reduction in the emission of gaseous
pollutants is provided.
[0011] From Combust. Flame 55 (1984), pages 53 to 58, it is also
known to influence combustion processes by way of electrical
discharges, in particular corona discharges. Here too, the result
is intended to be an improvement in the flame stability and a
reduction in the pollutant emission. One technical application of
the aforementioned effects is described in WO 96/01394 A1. The
common factor in all the methods described above is that the
electrodes which are needed in order to produce the electric field
or a discharge in the flame are in direct contact with the flame,
specifically with the effect that charge carriers from the flame
can reach the electrodes without hindrance.
[0012] The influence of electric fields on flames is based on the
fact that the charge carriers present in the flame or produced
therein by a discharge have forces exerted on them which displace
the charge carriers. This is equivalent to the flow of an electric
current. To turn the argument on its head, influencing a flame by
way of an electric field or an electric discharge is not possible
if no current can flow.
[0013] Investigations by the applicant have shown that, in order to
influence flames of engineering dimensions, i.e. necessary with
heating outputs in the range above 1 kW, electric field strengths
are needed which, because of the gas discharges induced in the
flame, require electric outputs which make the application of the
method uneconomic or technically impossible. In the extreme case,
an arc is formed within the flame. This applies primarily to DC
electric fields. However, even in the application corresponding to
the prior art of alternating electric fields or pulsed electric
fields, the formation of impermissible high-current discharges can
occur.
[0014] U.S. Pat. No. 3,416,870 A explains that a flame can be
influenced by electric devices without impermissibly high currents,
leading to a technically or economically unacceptable power
consumption occurring in the flame to be influenced. For this
purpose, the flame and at least one of the electrodes needed to
produce the field are separated from each other by an insulating
material in such a way that charge carriers from the flame cannot
reach the electrodes insulated in this way. A time-variable
voltage, that is to say in particular an alternating voltage or a
pulsating direct voltage, is applied between the insulated
electrode and a further electrode, which can be in contact with the
flame.
[0015] In the flame, it is possible for a current to flow until the
capacitance of the capacitor formed by the electrodes and the
insulating material is charged up or, expressed in other words,
until the opposing electric field built up by the displacement
current and the charge carrier accumulation effected by this
prevents further charge carrier transport. After the charges
accumulated on the surface of the insulating material during the
current flow phase have been transported away by loss mechanisms,
such as diffusion processes, a displacement current can flow again,
and there is a renewed action of the electric field on the
flame.
[0016] The same also results in principle from GB 1 013 015 A, in
which electric and/or magnetic fields act on the flame to the same
extent during the combustion process. Furthermore, EP 0 212 379 B1
discloses an arrangement for improving the combustion process in a
combustion power station, in which there is an ionizing element for
ionizing the gases involved in the combustion.
[0017] Experimental investigations on a device following the
principle of U.S. Pat. No. 3,416,870 A show that the effect of the
electric field depends on the mark-space ratio of the pulsed
voltage applied, in such a way that the effect that can be achieved
is greater the longer a voltage is actually applied, that is to say
the greater the mark-space ratio. Accordingly, the greatest effect
would be achieved if a direct voltage were to be applied, if a
current could also flow in this case. Since the flame is enclosed
by an insulating material enclosure, the application of a direct
voltage without further special measures does not cause a current
to flow and therefore remains without any effect in the intended
sense.
SUMMARY
[0018] An object of an embodiment of the invention includes
specifying an improved method and/or associated device with which
the combustion processes can be influenced positively in an
economic manner.
[0019] In an embodiment of the invention, the flame and the
electrodes are separated by an ion-conducting material. As such,
the charge carrier transport is limited. In this case, the
limitation of the charge carrier transport may advantageously be
carried out as a function of temperature, since the transition from
the insulating state to the conductive state is
temperature-dependent.
[0020] With an embodiment of the invention, the flame can be
influenced without impermissibly high currents, leading to a
technically or economically unacceptable power consumption,
occurring in the flame to be influenced. During the action of the
electric field on the flame, the charge carrier transport between
flame and electrodes is limited and the occurrence of independent
discharges, in particular arcs, is avoided. The result is a
stabilizing and/or pollutant-reducing action.
[0021] The specified effects are all realized in a device according
to an embodiment of the invention in that the flame and at least
one of the electrodes needed to produce the field are separated
from each other by an ion-conducting insulating material. As such,
charge carriers from the flame cannot reach the electrode insulated
in this way. The ion-conducting material used is either aluminum
oxide or, in particular, a zirconium oxide stabilized with
additives. Such additives are in particular yttrium oxide.
[0022] Additional advantages of an embodiment of the invention
result if the system is assigned sensors and control devices, which
control the voltage applied to the electrodes in such a way that
the combustion process is influenced in the desired manner. There
are preferably sensors of which one measures the frequency of any
combustion oscillations which may be present and another measures
the pollutant concentration. Sensors supply the input signal to a
control unit, which controls the frequency, amplitude and phase of
the voltage applied to the electrodes in such a way that the
combustion oscillations are minimized.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Further details and advantages of embodiments of the
invention emerge from the following figure description by using the
drawings.
[0024] FIGS. 1 to 3 show three different example embodiments of the
invention, in each case in a schematic sectional illustration.
[0025] In the figures, identical or identically acting parts have
the same designations. The figures will to some extent be described
jointly in the following text.
DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS
[0026] According to FIG. 1, the flame 2 produced by a burner 1 for
gaseous, liquid or prepared solid powdery fuels transported in
gases or liquids is enclosed by an insulating material enclosure 3
in such a way that the fuel enters the enclosure at one end 4 and
the waste combustion gas emerges on the other side 5. The
insulating material enclosure 3 includes an ion-conducting material
as a specific, high-temperature resistant ceramic material. Such a
material, at temperatures of a few hundred Kelvin such as those
reached in the vicinity of the gas flames in gas turbines, becomes
electrically conductive as a result of ion conduction.
[0027] A material with properties of this type is in particular
aluminum oxide or zirconium oxide stabilized with additives, which
have ion-conducting properties. In particular, the second-named
material is used in solid electrolyte ceramic high-temperature fuel
cells, which are also known as SOFC (Solid Oxide Fuel Cell). There,
this material permits the charge carrier transport--in this case
via the ion-conducting electrolyte--at sufficiently high
temperatures.
[0028] In FIG. 1, an electrode 6 is arranged inside the enclosure
3. The electrode 6 arranged inside the enclosure 3 can also be the
housing 1 or another electrically conductive part of the burner 1,
as illustrated in FIG. 2.
[0029] A further electrode 7 is arranged outside the enclosure 3.
There can also be a plurality of electrodes at the same or
different potential both inside and outside the enclosure 3, only
one inner and one outer electrode being mentioned in the following
text for the technical function, for reasons of simplicity.
[0030] In the example embodiments of FIGS. 1 and 3, the connections
between the electrodes 7 and 9 and the power supply unit 8 are
isolated electrically from the insulating material enclosure 3
which surrounds the burner chamber 5 by means of insulating
leadthroughs 12 and 13.
[0031] The electrodes, illustrated as toroidal annular electrodes
or else as cylindrical electrodes in the individual figures by way
of example, can also be designed in another suitable shape. In
particular, the electrodes can include films and be stuck to the
insulating material enclosure. Furthermore, the electrodes can be
vapor-deposited or sprayed onto the insulating material enclosure
by means of suitable methods.
[0032] In the figures, the electrodes 6, 7 and 1, 7 and,
respectively, 9, 11 are connected via feed lines to the power
supply unit 8, which supplies a direct voltage. One advantage of at
least one embodiment of the invention is that the device specified
also permits the application of an alternating voltage, a clocked
direct voltage, a pulsed voltage or any desired combinations
thereof.
[0033] The insulating material enclosure 3 can be designed such
that it encloses the combustion chamber 5, as indicated in the
example embodiments of FIGS. 1 and 2. However, it can also enclose
an individual flame or else a plurality of flames within a
combustion chamber. In a combustion chamber, a plurality of
insulating material enclosures with the electrodes assigned to the
latter can enclose one flame or in each case a plurality of
flames.
[0034] In the example embodiment of FIG. 3, the electrode 9 is
shielded from the flame 2 by being enclosed completely and in a
positive manner by an insulating material enclosure 10, while the
electrode 11 can be in direct contact with the flame.
[0035] Instead of the gaseous fuel, solids can also be treated in
the same way. In this case, it is important that smaller flames are
formed above the solid fuel, which is normally located on a grate,
are designated flamelets, as they are known, and are influenced in
the sense described above.
[0036] The substantial advantage of the arrangements described by
using the individual figures is that although the current through
the flame is sufficient to effect pollutant-reducing and
stabilizing effects, it always remains limited to such an extent
that the build-up of a high-current, powerful discharge is ruled
out.
[0037] To complete the examples illustrated in the figures, the
system can be assigned sensors and control devices: A first sensor
registers the frequency and/or amplitude of any combustion
oscillations that may be present. A second sensor measures the
pollutant concentration in the waste gas stream from the flame. The
sensors supply input signals to a control unit, which controls or
regulates the direct voltage applied to the electrodes and the
frequency, amplitude and phase of any alternating or pulsed voltage
which may be superimposed on the direct voltage, in such a way that
the combustion oscillations and the pollutant concentration in the
waste gas become a minimum.
[0038] Example embodiments being thus described, it will be obvious
that the same may be varied in many ways. Such variations are not
to be regarded as a departure from the spirit and scope of the
present invention, and all such modifications as would be obvious
to one skilled in the art are intended to be included within the
scope of the following claims.
* * * * *